Power equipments in a power system mainly are inductive equipments. Low power factors lead to serious line loss. In order to ensure an economic operation of a power grid, there is a parallel capacitor compensation device equipped to a main load side (10 kV or 35 kV) of each transformer substation of respective voltage grade. Positive reactive power produced by a perceptual device in the power grid constantly changes, so that negative reactive power produced by a corresponding compensation capacitor would also change correspondingly. Because it is easier to switch a reactor in a manner of fling-cut switching rather than to switch a capacitor, a capacitor is generally adopted to generate a static negative reactive power so as to adjust change of reactive power using a method of switching a reactor in a manner of fling-cut switching or adjusting a saturated electronic controller, which apparently causes complexity of a reactive power compensation equipment. Using a thyristor as a fling-cut switch can solve a fling-cut switching problem of a capacitor (a SVC technology); and although thyristor fling-cut switching can avoid an inrush current during capacitor fling-cut switching, the capacitor fling-cut switching has a defect of high power consumption and high cost. At present, in an occasion that a frequency of the capacitor fling-cut switching is not high, a commonly adopted manner is to adopt vacuum circuit breaker for fling-cut switching; however, the vacuum circuit breaker cannot avoid an inrush current during fling-cut switching. A thyristor fling-cut switch would be turned on by mistake when a dv/dt is very large, so that a vacuum circuit breaker would produce an inrush current during fling-cut switching. To solve such a problem, series reactors are generally adopted to suppress surge voltage and surge current, which will increase cost of a compensation device. A Chinese patent application No. 201110034379.4 has disclosed a high-voltage electronic arc extinguishing switch, which is formed of a plurality of switch contacts in series; however, this application requires that a withstand voltage between each relay contact and control coils should be over a controlled total voltage, which places great demands on insulation between contacts of a relay and coils.
When a high-voltage capacitor performs a reactive power compensation task, a high-voltage capacitor as a reactive load has to be connected to a power grid with a high-voltage switch. An existing high-voltage capacitor and high-voltage switch are two separate components, as shown in FIG. 1, where the high-voltage capacitor is generally composed of a plurality of capacitor core packages in series or parallel, the high-voltage switch is a switch having a single contact, and one high-voltage switch controls one high-voltage capacitor, or a plurality of series or parallel high-voltage capacitor. For security reasons regarding a high-voltage AC capacitor, many detection and protection devices for capacitor are generally installed in a compensation equipment; however, these detection and protection devices are external and are unable to detect operating situations inside the capacitor, thus so-called protection is lagging and inaccurate.
For security reasons regarding a traditional high-voltage capacitor, discharging devices must be arranged in parallel at both ends of the capacitor. Although there is a low cost due to use of discharging resistor, a great power consumption would occur. Therefore, a discharging coil with high cost is generally connected to both ends of an AC capacitor in parallel; however, the discharging coil would also produce certain power consumption during operation of a compensation capacitor.
Even though a capacitor for reactive power compensation on a power grid, and a fling-cut switch are always used together, but they always appear as two components, which increases not only hidden danger due to poor connection between the two components, but also cost of the two components. In addition, it is not easy for actual designers and users of a reactive power compensation capacitor to select a proper fling-cut switch, since different capacitors in use need to be coordinated with different fling-cut switches.
A high-voltage capacitor is formed of a plurality of low-voltage capacitor core packages in series, and a traditional high-voltage capacitor is formed of gold foil capacitor core packages in series. Capacitor core packages produced by a thin film metalizing process are widely used in a low-voltage field due to advantages of cost and environmental protection; however, capacitor core packages produced by the thin film metalizing process cannot be used in a field of high-voltage capacitors since a thin film metalized capacitor in use continually decays in capacity, and a capacitor core package decayed in capacity would further accelerate decay in capacity due to increasing of a partial pressure if thin film metalized capacitors are connected in series, so that lives of thin film metalized capacitor core packages connected in series in a high-voltage capacitor are short.